Strut-and-Tie Model for Shear Friction of Concrete with Fiber-Reinforced Polymer Composites

Analytical models are developed from tests of shear transfer units strengthened externally with carbon fiber-reinforced polymer (CFRP) composite strips. The analytical models are based on superposition of the two components of shear friction strength: that due to concrete and that due to concrete-CFRP interaction. The simplified model, based on experimental observations, was used to separate the shear friction contribution of concrete and that of concrete-CFRP interaction. The strut-and-tie model depends on the effective CFRP tensile strain, which is a function of the normalized CFRP stiffness. The strut-and-tie model can capture the shear friction contribution due to the tensioning effect of the CFRP strip. This is a novel application of the strut-and-tie model in externally applied CFRP composites for concrete under shear friction, and it is successful in representing the experimental behavior with good accuracy.